IntelliJ has very good IDEs. But their IDEs would be even better were they native OS X applications. For example, you can't use the Mac OS X services like "Look up in a dictionary" in IntelliJ.
For me, it's the open and save dialogs that bother me most. I quite like the editor, especially as compared to Eclipse, but for source editing, I'd rather use one the OS X editors like TextMate or BBEdit.